It does require an initial investment but it does not have to be super expensive. I try to take into account that with an RV equipped with solar you don't have to pay for campgrounds every night. If you look at it that way a 100w solar panel will be paid for in just a few nights. The same is true for a good battery. A week of boondocking will save enough money to get what you need for a small 100w system with a panel, controller and cables.
If you want to power your house with solar that is a different story. It still might be worth it depending on how much you can save on your energy bill and how long it will take to "earn back" the initial investment.